Given an array of strings, return all groups of strings that are anagrams. http://www.leetcode.com/onlinejudge

leetcode_anagrams.cpp

#include <algorithm>
#include <vector>
#include <string>
#include <tr1/unordered_map>
using namespace std;

class Solution {
public:    
    vector<string> anagrams(vector<string> &strs) {
        vector<string> ret;
        tr1::unordered_map<string, int> flag;
        tr1::unordered_map<string, int>::iterator it;
        for (int i = 0; i < strs.size(); ++i) {
            string tmp = strs[i];
            sort(tmp.begin(), tmp.end());
            it = flag.find(tmp);
            if (it == flag.end()) {
                flag[tmp] = i;
            }
            else {
                if (it->second != -1) {
                    ret.push_back(strs[it->second]);
                }
                ret.push_back(strs[i]);
                it->second = -1;
            }
        }
        return ret;
    }
};